![]() There is some controversy of when and where the 2-transistor topology appeared: the Tone Bender MK1.5 is similar to the Dick Denney designed Vox Distortion Booster circuit, nearly identical to the Italian made Vox Tone Bender circuit, and the Arbiter Fuzz Face circuit. The fuzz face design was inspired in other contemporary fuzz pedals like the Maestro Fuzz Tone (designed by Glen Snotty) and the Sola Sound ToneBender (designed by Gary Hurst) although the Fuzz Face was an easier circuit than the competitors with only 2 transistors instead of 3. The last block (the Feedback Network) will affect the rest of the analysis because it will influence the most important parameters: voltage gain, input impedance, output impedance and frequency response. It can be broken down into three parts: Input Stage, Output Stage and Feedback Network. The circuit is a simple 2 stage amplifier with a feedback network path. There are some circuits that help to measure the transistor gain. However, there are some other options, for a more compressed sound you can use β=90-120 for Q 1 and β=150-190 Q 2. This gain variation is crucial in the design, the best match uses a low gain in the first stage (β=70-80 approx.) and a high gain in the second stage (β=110-130 approx.). ![]() Germanium transistors tend to have high leakage current and an inconsistent gain value. Germanium Transistor Selection: It is important to select the right transistor from the whole batch in order to archive the best effect performance. Cornell explains why the production switched to the modern, temperature independent, cheaper and stable silicon transistors like the BC183L, BC183KA, BC130C, BC108C, BC109C, BC209C, and BC239C. "There were always problems with them, so I’d get involved in testing and repairing because they just didn’t all work right!" I think the Arbiter-England one didn’t use the NKT275 germanium transistor in those days we used the AC128." Germanium transistors are considered to have an overall better sounding to this effect with some drawbacks: germanium manufacturing is not as consistent and controlled as silicon and they have shorter lifespan and more temperature sensitivity.ĭennis Cornell: "All the transistors worked in a very similar way and all did the job, but they did give a slightly different tone.
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